The present disclosure relates generally to fluidized solids distributors. More specifically, in certain embodiments, the present disclosure relates to spent catalyst distributors useful in fluid catalytic cracking operations and associated methods and systems.
In a typical Fluid Catalytic Cracking Unit (FCCU), finely divided regenerated catalyst may be drawn from a regenerator through a regenerator standpipe and may contact a hydrocarbon feedstock in a lower portion of a reactor riser. Hydrocarbon feedstock and steam may enter the riser through feed nozzles. The mixture of feed, steam and regenerated catalyst, which may have a temperature in the range of from about 200° C. to about 800° C., may pass up through the riser reactor, converting the feed into lighter products while a coke layer may deposit on the surface of the catalyst, temporarily deactivating the catalyst.
The hydrocarbon vapours and catalyst from the top of the riser may then be passed through cyclones to separate spent catalyst from the hydrocarbon vapour product stream. The spent catalyst may enter a stripper where steam may be introduced to remove hydrocarbon products from the catalyst. The spent catalyst may then pass through a spent catalyst transfer line to enter the regenerator where, in the presence of air and at a temperature in the range of from about 620° C. to about 760° C., the coke layer on the spent catalyst may be combusted to restore the catalyst activity. Regeneration may be performed in a fluidized bed. The regenerated catalyst may then be drawn from the regenerator fluidized bed through the regenerator standpipe and, in repetition of the previously mentioned cycle, contact the feedstock in the reactor riser.
Catalyst regeneration is a critical step in FCCU operations. The success of the step may depend on the contacting efficiency between the spent catalyst and oxygen-containing gas in the regenerator. Catalyst may be injected into the regenerator in a number of different ways. One conventional way of introducing catalyst into a regenerator is injecting the catalyst through a side entry port. An example of a conventional device used for introducing catalyst into a regenerator is a spent catalyst inlet device (SCID). Typically, in a SCID system, the spent catalyst is transported to the regenerator in the dense phase. Examples of SCID systems are described in U.S. Pat. No. 6,797,239, the entirety of which is hereby incorporated by reference.
While SCID systems may be effective, such side entry spent catalyst distribution systems may have issues with providing even distribution of spent catalyst within the regenerator. It is desirable to develop an entry system that promotes more even distribution of spent catalyst within the regenerator and also avoids air grid interference.